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Kim, Munjeong, Juyoung Kim, Young Min Jo i Jong-Ki Jeon. "Decomposition of Hydroxylammonium Nitrate Solution Over Nanoporous CuO Supported on Honeycomb". Journal of Nanoscience and Nanotechnology 21, nr 8 (1.08.2021): 4532–36. http://dx.doi.org/10.1166/jnn.2021.19438.
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We investigated the influence of a copper loading strategy over a honeycomb structure on the catalytic performance during the decomposition of a hydroxylammonium nitrate (HAN) aqueous solution. Copper was supported on the honeycomb surface by means of a metal coating method (MC), i.e., a method of directly coating a metal, and a metal alumina coating method (MAC), i.e., a method of coating a mixture of metal and alumina. The properties of the catalysts were analyzed by N2 adsorption, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The Cu(16.8)/honeycomb-MC catalyst showed a lower decomposition onset temperature during the decomposition of the HAN aqueous solution compared to that over the Cu(7.0)/honeycomb- MAC catalyst, an outcome ascribed to the higher copper loading and the higher dispersion of copper in the Cu(16.8)/honeycomb-MC catalyst compared to that in the other catalyst. The Cu(16.8)/honeycomb-MC catalyst was confirmed to have both excellent activity and heat resistance during the decomposition of a HAN aqueous solution.
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Agnihotri, Ruchika, i Charlie Oommen. "Cerium oxide based active catalyst for hydroxylammonium nitrate (HAN) fueled monopropellant thrusters". RSC Advances 8, nr 40 (2018): 22293–302. http://dx.doi.org/10.1039/c8ra02368a.
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Yoo, Dalsan, Jaegyu Woo, Seolyeong Oh i Jong-Ki Jeon. "Performance of Pt and Ir Supported on Mesoporous Materials for Decomposition of Hydroxylammonium Nitrate Solution". Journal of Nanoscience and Nanotechnology 20, nr 7 (1.07.2020): 4461–65. http://dx.doi.org/10.1166/jnn.2020.17598.
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The catalytic decomposition of hydroxylammonium nitrate (HAN) was investigated using a series of platinum and iridium supported on mesoporous materials. In this study, MMZY, KIT-6, and SBA-15 were used as supports. The effects of the active metal and the pore structure of the catalysts on decomposition of HAN solution were studied. The activity of the platinum catalysts supported on mesoporous material is much superior to that of the iridium catalysts on the same support. The Pt(10)/SBA-15 catalyst showed excellent decomposition activity and was the best among the catalysts tested here, which seemed to be because of the pore structure of Pt(10)/SBA-15. Because the pore size of Pt(10)/SBA-15 is larger than that of Pt(10)/MMZY and Pt(10)/KIT-6, it is more advantageous for diffusion of reactant and product gas. The activity of the catalyst increased as the amount of Pt loaded on the SBA-15 support increased.
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Woo, Jaegyu, Dalsan Yoo, Seolyeong Oh i Jong-Ki Jeon. "Decomposition of Energetic Ionic Liquid Over IrCu/Honeycomb Catalysts". Journal of Nanoscience and Nanotechnology 20, nr 11 (1.11.2020): 7065–69. http://dx.doi.org/10.1166/jnn.2020.18841.
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The objective of this study is to elucidate the influence of a loading procedure of iridium and copper oxides over cordierite honeycomb support on catalytic performance during the decomposition of a hydroxylammonium nitrate (HAN) solution. Iridium and copper composite oxides were successfully supported on the cordierite honeycomb at the same time by repeating the wash coating process more than 2 times. Through the wash coating process, Cu and Ir were supported up to 43.4% and 4.9%, respectively. The cordierite honeycomb without active metal plays little role as a catalyst to lower the decomposition temperature. It was found that IrCu/honeycomb-2 catalyst, which was prepared by repeating the wash coating procedure twice, is an optimal catalyst for the decomposition of HAN solution. The IrCu/honeycomb-2 catalyst had the effect of lowering the decomposition onset temperature by 27.1°C compared to thermal decomposition.
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Agnihotri, Ruchika, i Charlie Oommen. "Evaluation of hydroxylammonium nitrate (HAN) decomposition using bifunctional catalyst for thruster application". Molecular Catalysis 486 (maj 2020): 110851. http://dx.doi.org/10.1016/j.mcat.2020.110851.
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Bamufleh, Hisham S., i Sharif F. Zaman. "Ammonia Decomposition over Alkali Metal (Li, K, Cs)-Promoted Bulk Mo2N Catalyst". Processes 11, nr 8 (30.07.2023): 2287. http://dx.doi.org/10.3390/pr11082287.
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Ammonia (NH3), which has a 17.7 wt% gravimetric hydrogen density, has been considered as a potential hydrogen storage material. This study looked at the thermocatalytic decomposition of NH3 using a bulk Mo2N catalyst that was boosted by alkali metals (AM: 5 wt% Li, K, Cs). The K-Mo2N catalyst outperformed all other catalysts in this experiment in terms of catalytic performance. At 6000 h−1 GHSV, 100% conversion of NH3 was accomplished using the K-Mo2N, Cs-Mo2N, and Mo2N catalysts. However, when compared to other catalysts, K-Mo2N had the highest activity, or 80% NH3 conversion, at a lower temperature, or 550 °C. The catalytic activity exhibited the following trend for the rate of hydrogen production per unit surface area: K-Mo2N > Cs-Mo2N > Li-Mo2N > Mo2N. Up to 20 h of testing the K-Mo2N catalyst at 600 °C revealed no considerable deactivation.
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Inoue, Masashi, Kouta Asai, Yoshiyuki Nagayasu, Koji Takane i Eriko Yagasaki. "Synthesis of Carbon Nanotubes by the Catalytic Decomposition of Methane". Advances in Science and Technology 48 (październik 2006): 67–72. http://dx.doi.org/10.4028/www.scientific.net/ast.48.67.
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The influence of morphology of the support particles upon the nickel-catalyzed decomposition of methane into carbon nanotubes and hydrogen was explored using a thermogravimetric apparatus. High carbon nanotube yield was attained by the Ni catalysts supported on the glycothermally synthesized ZrO2 and Er3Ga5O12 particles, which had spherical shapes. Quite high carbon yield was also obtained by the Ni catalyst supported on spherical Al2O3 particles (Nanophase Tech. Corp.). It was concluded that the most important factor governing the carbon yield is the morphology of the catalyst support, which contributes to the internal pressure of carbon nanotubes thus determining their chemical potentials.
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Liu, Lai Bao, Deng Liang He i Dong Mei Zhao. "Study on Photocatalysis Degradation of Phenol by Using Tourmaline/ TiO2 System as Catalyst". Advanced Materials Research 399-401 (listopad 2011): 1337–41. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.1337.
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The authors use the method of titanium salts on the surface of tourmaline particles hydrolyzing and coating TiO2 to construct Tourmaline/ TiO2 system in different conditions and characterize the catalyst system by TEM and SEM and Raman Spectra Pattern. The writers used phenol solution as the target compound to observe the removing effects of catalysis system on phenol under dynamic conditions. The results showed that: a. the compound photo catalysis system had brilliant decomposition performance on phenol. b. It would reach high decomposition efficiency on the initial phase of reaction when the rate of tourmaline to TiO2 was 1:1 and the decomposition efficiency could be 96.29% at 120min when the rate was 0.2, which was 26% higher than that of pure phase TiO2.
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Villamarin-Barriga, Estefanía, Jéssica Canacuán, Pablo Londoño-Larrea, Hugo Solís, Andrés De La Rosa, Juan F. Saldarriaga i Carolina Montero. "Catalytic Cracking of Heavy Crude Oil over Iron-Based Catalyst Obtained from Galvanic Industry Wastes". Catalysts 10, nr 7 (3.07.2020): 736. http://dx.doi.org/10.3390/catal10070736.
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Sewage sludge from the galvanic industry represents a problem to the environment, due to its high metal content that makes it a hazardous waste and must be treated or disposed of properly. This study aimed to evaluate the sludge from three galvanic industries and determine its possible use as catalysts for the synthesis of materials. Catalyst was obtained from a thermal process based on dried between 100–120 °C and calcination of sludges between 400 to 700 °C. The physical–chemical properties of the catalyst were analyzed by several techniques as physisorption of N2 and chemisorption of CO of the material. Catalytic activity was analyzed by thermogravimetric analysis of a thermo-catalytic decomposition of crude oil. The best conditions for catalyst synthesis were calcination between 400 and 500 °C, the temperature of reduction between 750 and 850 °C for 15 min. The catalytic material had mainly Fe as active phase and the specific surface between 17.68–96.15 m2·g−1, the catalysts promote around 6% more weight-loss of crude oil in the thermal decomposition compared with assays without the catalyst. The results show that the residual sludge of galvanic industries after thermal treatment can be used as catalytic materials due to the easiness of synthesis procedures required, the low E-factor obtained and the recycling of industrial waste promoted.
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Shen, Bo Xiong, Ting Liu, Ning Zhao, Juan Ma i Xiao Cui Hao. "Research of Catalytic Performance over Transition Metal Modified MnOx-CeOx/ACF Catalysts". Advanced Materials Research 383-390 (listopad 2011): 1945–50. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.1945.
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The catalyst of MnOx-CeOx/ACF prepared by impregnation method was used for low-temperature selective catalytic reduction (SCR) of NO with NH3, and more than 90% NO conversion was obtained at 230°C. Fe、Cu or V was used respectively to prepare transition metal modified MnOx-CeOx/ ACF catalysts which had lower catalytic activity than that over MnOx-CeOx/ACF. SEM, N2 adsorption and NH3-TPD were used to analyze the catalysts. The results showed that transition metal modified catalysts had a reduced surface area, pore volume and surface acidity. SO2 had a negative effect on SCR performance of the catalysts. Fe modified catalyst exhibited SO2 tolerance in the first 6h in the presence of 100ppm SO2. Thermal treatment in N2 at 350°C was used to regenerate the deactivated catalysts by SO2. The decomposition of ammonium salts recovered the catalytic activity to some extent. The sulfated active components in deactivated catalysts after the thermal treatment enhanced the surface acidity of the catalysts.
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Liang, Wenjun, Xiaoyan Du, Yuxue Zhu, Sida Ren i Jian Li. "Catalytic Oxidation of Chlorobenzene over Pd-TiO2 /Pd-Ce/TiO2 Catalysts". Catalysts 10, nr 3 (20.03.2020): 347. http://dx.doi.org/10.3390/catal10030347.
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A series of Pd-TiO2/Pd-Ce/TiO2 catalysts were prepared by an equal volume impregnation method. The effects of different Pd loadings on the catalytic activity of chlorobenzene (CB) were investigated, and the results showed that the activity of the 0.2%-0.3% Pd/TiO2 catalyst was optimal. The effect of Ce doping enhanced the catalytic activity of the 0.2% Pd-0.5% Ce/TiO2 catalyst. The characterization of the catalysts using BET, TEM, H2-TPR, and O2-TPD showed that the oxidation capacity was enhanced, and the catalytic oxidation efficiency was improved due to the addition of Ce. Ion chromatography and Gas Chromatography-Mass Spectrometer results showed that small amounts of dichlorobenzene (DCB) and trichlorobenzene (TCB) were formed during the decomposition of CB. The results also indicated that the calcination temperature greatly influenced the catalyst activity and a calcination temperature of 550 °C was the best. The concentration of CB affected its decomposition, but gas hourly space velocity had little effect. H2-TPR indicated strong metal–support interactions and increased dispersion of PdO in the presence of Ce. HRTEM data showed PdO with a characteristic spacing of 0.26 nm in both 0.2% Pd /TiO2 and 0.2% Pd-0.5% Ce/TiO2 catalysts. The average sizes of PdO nanoparticles in the 0.2% Pd/TiO2 and 0.2% Pd-0.5% Ce/TiO2 samples were 5.8 and 4.7 nm, respectively. The PdO particles were also deposited on the support and they were separated from each other in both catalysts.
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Amariei, Daniel, Sylvie Rossignol i Charles Kappenstein. "Shape Forming of Alumina-Silica of High Thermal Stability for Space Propulsion Applications". Advances in Science and Technology 45 (październik 2006): 427–35. http://dx.doi.org/10.4028/www.scientific.net/ast.45.427.
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The replacement of toxic hydrazine used for catalytic propulsion by less toxic propellants such as ionic liquids is of hot interest. The challenge for this replacement is the formulation, development and shape forming of new catalysts. Efficient catalysts for the decomposition of aqueous 79 wt.-% HAN solutions (hydroxylammonium nitrate NH3OH+NO3 -) contain 10 wt.-% Pt active phase deposited on a support. Laboratory-made powder catalysts contain platinum supported on Si-doped alumina and display a good activity at low temperature. But, for industrial applications in propulsion thrusters, the pressure drop due to a powder is too high and consequently shape formed supports and catalysts must be prepared and investigated. Two catalyst types have been prepared (i) from shaped supports obtained at the laboratory level using the “oil-drop” method and (ii) from supports formed through an industrial procedure. Both shape formed samples display comparable properties as the powder support, such as high thermal stability linked to the presence q and d aluminas and similar BET surface area. Catalysts based on these supports show efficient catalytic activities.
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Li, Ze, Jie-Ying Jing, Zhi-Qiang Qie i Wen-Ying Li. "Influence of Reduction Temperature on the Structure and Naphthalene Hydrogenation Saturation Performance of Ni2P/Al2O3 Catalysts". Crystals 12, nr 3 (24.02.2022): 318. http://dx.doi.org/10.3390/cryst12030318.
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Jet fuel rich in hydroaromatics and cycloalkanes could be derived from direct coal liquefaction oil via the hydrogenation saturation process. Developing an efficient catalyst to transform naphthalene hydrocarbons to hydroaromatics and cycloalkanes with high selectivity plays a significant role in realizing the above hydrogenation saturation process. In this work, Ni2P/Al2O3 catalysts were prepared at different reduction temperatures via the thermal decomposition of hypophosphite. We investigated the influence of reduction temperature and the results showed that reduction temperature had an important impact on the properties of Ni2P/Al2O3 catalysts. When the reduction temperature was 400 °C, the Ni2P particle size of the Ni2P/Al2O3 catalyst was 3.8 nm and its specific surface area was 170 m2/g. Furthermore, the Ni2P/Al2O3 catalyst reduced at 400 °C obtained 98% naphthalene conversion and 98% decalin selectivity. The superior catalytic activity was attributed to the smaller Ni2P particle size, higher specific surface area and suitable acidity, which enhanced the adsorption of naphthalene on Ni2P/Al2O3 catalyst.
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Yan, Qiangu, Jinghao Li, Xuefeng Zhang, Jilei Zhang i Zhiyong Cai. "Synthetic Bio-Graphene Based Nanomaterials through Different Iron Catalysts". Nanomaterials 8, nr 10 (16.10.2018): 840. http://dx.doi.org/10.3390/nano8100840.
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Kraft lignin was catalytically graphitized to graphene-based nanostructures at 1000 °C under argon atmosphere with four iron catalysts, iron(III) nitrate (Fe-N); iron(II) chloride (Fe-Cl2); iron(III) chloride (Fe-Cl3); and iron(II) sulfate (Fe-S). The catalytic decomposition process of iron-promoted lignin materials was examined using thermalgravimetric analysis and temperature-programmed decomposition methods. The crystal structure, morphology and surface area of produced materials were characterized by means of X-ray diffraction, Raman, scanning electron microscopy, high resolution transmission electron microscopy and N2 adsorption−desorption techniques. Experimental results indicated that iron nitrate catalyst had better iron dispersion three other iron salts. Iron nitrate was the most active catalyst among four iron salts. The low activity of iron in iron chloride-promoted samples was because the residual chlorine over iron surfaces prevent iron interaction with lignin functional groups.
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Vasic, Marija, Marjan Randjelovic, Jelena Mitrovic, Nikola Stojkovic, Branko Matovic i Aleksandra Zarubica. "Decolorization of crystal violet over TiO2 and TiO2 doped with zirconia photocatalysts". Chemical Industry 71, nr 3 (2017): 259–69. http://dx.doi.org/10.2298/hemind160521036v.
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Titania based catalyst and TiO2 doped with zirconia were prepared by modified sol?gel method. The synthesized catalysts samples were characterized by BET, XRD, SEM and FTIR techniques. Photocatalytic activity was tested in the reaction of crystal violet (CV) dye decolorization/decomposition under UV light irradiation. The effect of several operational parameters, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment and number of reaction cycles were also considered. The obtained results indicated faster dye decolorization with the increase of the catalyst amount and a decrease of initial CV concentrations. An influence of doping with zirconia on the physico-chemical properties of bare titania was studied. The doping procedure had affected photocatalytic properties of the final catalytic material, and had improved photocatalytic performances of doped catalyst on crystal violet decolorization/degradation in comparison to bare titania.
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Xu, Wenying, i Haoyang Gao. "Decomposition performance of hypochlorite on bead-type NiOx(OH)y catalyst: improving applicability of catalysts". Water Science and Technology 82, nr 5 (24.08.2020): 967–83. http://dx.doi.org/10.2166/wst.2020.402.
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Abstract An easy-to-use, pollution-free and reusable beaded NiOx(OH)y catalyst for improving hypochlorite oxidation was prepared by impregnating the mixture of persulfate and alkali over alumina and then reduced it with Ni2+. The effects of catalyst preparation conditions and reaction parameters on NaClO conversion rate and Ni2+ dissolution rate were studied. Impregnating the γ-Al2O3 beads in PS/OH− mixed solution with 0.59 M PS and PS/OH− molar ratio of 1.1, and then reducing with 0.8 M Ni2+ solution is the best condition for preparing catalyst. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The best catalytic layer is characterized by high content of chemisorbed oxygen which can be converted into atomic oxygen. The hypochlorite conversion rate increased with the catalyst dosage and reuse times, and decreased with available chlorine, while pH of hypochlorite solution had little effect on the conversion rate. After running stably for 120 h in continuous flow test, the chemisorbed oxygen content in the optimal catalytic layer decreased slightly. Atomic oxygen plays an important role in the decolorization of dye solution by NaClO/NiOx(OH)y system. The oxidant consumption cost of this process is much cheaper than Fenton reagent. The prepared catalyst has great potential in hypochlorite decomposition and wastewater treatment.
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McCullough, Katherine, Pei-Hua Chiang, Juan D. Jimenez i Jochen A. Lauterbach. "Material Discovery and High Throughput Exploration of Ru Based Catalysts for Low Temperature Ammonia Decomposition". Materials 13, nr 8 (16.04.2020): 1869. http://dx.doi.org/10.3390/ma13081869.
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High throughput experimentation has the capability to generate massive, multidimensional datasets, allowing for the discovery of novel catalytic materials. Here, we show the synthesis and catalytic screening of over 100 unique Ru-Metal-K based bimetallic catalysts for low temperature ammonia decomposition, with a Ru loading between 1–3 wt% Ru and a fixed K loading of 12 wt% K, supported on γ-Al2O3. Bimetallic catalysts containing Sc, Sr, Hf, Y, Mg, Zr, Ta, or Ca in addition to Ru were found to have excellent ammonia decomposition activity when compared to state-of-the-art catalysts in literature. Furthermore, the Ru content could be reduced to 1 wt% Ru, a factor of four decrease, with the addition of Sr, Y, Zr, or Hf, where these secondary metals have not been previously explored for ammonia decomposition. The bimetallic interactions between Ru and the secondary metal, specifically RuSrK and RuFeK, were investigated in detail to elucidate the reaction kinetics and surface properties of both high and low performing catalysts. The RuSrK catalyst had a turnover frequency of 1.78 s−1, while RuFeK had a turnover frequency of only 0.28 s−1 under identical operating conditions. Based on their apparent activation energies and number of surface sites, the RuSrK had a factor of two lower activation energy than the RuFeK, while also possessing an equivalent number of surface sites, which suggests that the Sr promotes ammonia decomposition in the presence of Ru by modifying the active sites of Ru.
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Huh, Jeongmoo, Botchu V. S. Jyoti, Yongtae Yun, M. N. Shoaib i Sejin Kwon. "Preliminary Assessment of Hydrogen Peroxide Gel as an Oxidizer in a Catalyst Ignited Hybrid Thruster". International Journal of Aerospace Engineering 2018 (30.12.2018): 1–14. http://dx.doi.org/10.1155/2018/5630587.
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In regard to propulsion system applications, the stability of liquid propellants in long-term storage is of increasing importance, and this had led to a greater interest in gelation technology. As part of a preliminary test to determine the feasibility of using a gel propellant in a rocket with a catalyst bed, a hybrid rocket with a catalyst reactor using a gel propellant as an oxidizer was tested for the first time in this study. Experiments were conducted with two different oxidizers: one with liquid phase hydrogen peroxide and the other with gel phase hydrogen peroxide, as well as high-density polyethylene as fuel for a 250 N class hybrid thruster performance test. The thruster was designed with the catalyst ignition system, and a catalyst was manufactured to be inserted into the catalyst reactor to facilitate oxidizer decomposition. While the test result with neat hydrogen peroxide indicated sufficient decomposition efficiency using a manganese dioxide/alumina catalyst and successful autoignition of the fuel via the decomposed product, gel hydrogen peroxide exhibited insufficient decomposition and there were difficulties in operating the thruster as a part of the catalyst was covered in the gelling agent. This preliminary study identifies the potential challenges of using a gel phase oxidizer in a catalyst ignited hybrid thruster and discusses the technical issues that should be addressed in regard to a gel propellant hybrid thruster design with a catalyst reactor.
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Touati, Houcine, Sabine Valange, Marc Reinholdt, Catherine Batiot-Dupeyrat, Jean-Marc Clacens i Jean-Michel Tatibouët. "Low Temperature Catalytic Oxidation of Ethanol Using Ozone over Manganese Oxide-Based Catalysts in Powdered and Monolithic Forms". Catalysts 12, nr 2 (28.01.2022): 172. http://dx.doi.org/10.3390/catal12020172.
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Catalytic oxidation of low concentrations of ethanol was investigated in dry and humid air streams at low temperature (60 °C) over manganese oxide-based catalysts supported on a meso–macrostructured TiO2 using ozone as the oxidant. Ethanol was selected as a representative model VOC present in indoor air, and its concentration was fixed to 10 ppm. For that purpose, a series of Mn/TiO2 powder and monolithic catalysts was prepared, some doped with 0.5 wt% Pd. Whatever the catalyst, the presence of water vapor in the gas phase had a beneficial effect on the conversion of ethanol and ozone. The Pd–Mn/TiO2 catalyst containing 0.5 wt% Pd and 5 wt% Mn exhibited superior oxidation efficiency to the Mn/TiO2 counterparts by increasing ozone decomposition (77%) while simultaneously increasing the selectivity to CO2 (85%). The selectivity to CO2 approached nearly 100% by increasing the amount of catalyst from 20 to 80 mg. In a further step, alumina wash-coated cordierite honeycomb monoliths were coated with the 0.5Pd–5Mn/TiO2 catalyst. Full conversion of ethanol to CO2 without residual O3 emitted (less than 10 ppb) could be attained, thereby demonstrating that the proposed Pd–Mn/TiO2 monolithic catalyst fulfills the specifications required for onboard systems.
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Fedorova, Zaliya A., Vadim A. Borisov, Vera P. Pakharukova, Evgeniy Y. Gerasimov, Vladimir D. Belyaev, Tatyana I. Gulyaeva, Dmitriy A. Shlyapin i Pavel V. Snytnikov. "Layered Double Hydroxide-Derived Ni-Mg-Al Catalysts for Ammonia Decomposition Process: Synthesis and Characterization". Catalysts 13, nr 4 (30.03.2023): 678. http://dx.doi.org/10.3390/catal13040678.
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Layered Ni-Mg-Al hydroxides with (Ni + Mg)/Al = 2.5 differing in Mg/Ni ratios and related oxide systems have been synthesized and characterized. Ni-Mg-Al hydroxides were prepared by the coprecipitation method. It was found that the samples dried at 110 °C were layered Ni-Mg-Al hydroxides with a hydrotalcite-type structure. After the heat treatment at 600 °C, the formation of Ni-Mg-Al-mixed oxides with a specific nanostructure, an intermediate between a NaCl and spinel structure, took place. According to XRD data, it had the unit cell parameter a = 4.174–4.181 Å, and a crystallite size of 4.0 nm. The specific surface area of the Ni-Mg-Al samples dried at 110 °C was 45–54 m2/g, and that of those calcined at 600 °C was 156.1–209.1 m2/g. In agreement with HRTEM data, in all the synthesized nickel catalysts reduced at 700 °C (H2), particle size was mainly distributed between 15–20 nm. The catalyst activity of LDH-derived Ni-Mg-Al catalysts in ammonia decomposition was studied in a fixed-bed flow-type reactor at an atmospheric pressure within the temperature range 500–700 °C. The synthesized catalysts overcame existing analogues in catalytic performance. At a process temperature of 500 °C, the Ni2Mg3Al2-HT catalyst showed that the H2 productivity was 23.8 mmol/(gcat·min), exceeding the respective value of nickel catalysts reported in the literature.
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Broemmelsiek, Emil J., Joshua L. Rovey i Steven P. Berg. "Effect of Metal Sequestrants on the Decomposition of Hydroxylammonium Nitrate". Catalysts 11, nr 12 (4.12.2021): 1488. http://dx.doi.org/10.3390/catal11121488.
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Hydroxylammonium nitrate (HAN) is an energetic salt used in flight-proven green monopropellants such as ASCENT (formerly AF-M315E), flown in NASA’s 2019 Green Propellant Infusion Mission, and SHP163, flown in JAXA’s Rapid Innovative Satellite Technology Demonstration-1. The decomposition of HAN is catalyzed by metals commonly found in storage tanks, a factor limiting its use. This work investigates the ability of metal-sequestering chelating agents to inhibit the decomposition of HAN. Isothermal and dynamic thermogravimetric analysis (TGA) were used to find isothermal decomposition rates, decomposition onset temperatures, and first-order Arrhenius reaction rate parameters. In the present research, 2,2′-bipyridine (Bipy), triethanolamine (TEA), and ethylenediaminetetraacetic acid (EDTA) were studied as 0.05, 0.1, 0.5, 1, and 5% by weight additives in 90% aqueous HAN. An isothermal decomposition rate of 0.137%/h at 348 K was observed for HAN. The addition of 1% Bipy and 1% TEA reduced the isothermal decomposition rate by 20.4% to 0.109%/h, and by 3.65% to 0.132%/h, respectively, showing that Bipy can inhibit decomposition. The addition of 1% EDTA increased the isothermal decomposition rate by 12.4% to 0.154%/h. Bipy was found to increase the decomposition onset temperature from 454.8 K to 461.8 K, while the results for TEA and EDTA were inconclusive. First order reaction rates calculated by the Ozawa-Flynn-Wall method were found to be insufficient to capture the effects of the tested additives. Bipy was found to inhibit the decomposition of HAN, while TEA and EDTA produced little or negative effect, a result believed to be due to poor metal complex stability at low pH and high acidity, respectively. Spectrophotometry, used for colorimetric analysis of Bipy+iron complexes, showed that Bipy forms chelate complexes with trace iron impurities when added to HAN solutions.
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Chen, Shuang, Shukun Wang, Yunyun Dong, Hongmei Du, Jinsheng Zhao i Pengfang Zhang. "Anchoring NiO Nanosheet on the Surface of CNT to Enhance the Performance of a Li-O2 Battery". Nanomaterials 12, nr 14 (13.07.2022): 2386. http://dx.doi.org/10.3390/nano12142386.
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Li2O2, as the cathodic discharge product of aprotic Li-O2 batteries, is difficult to electrochemically decompose. Transition-metal oxides (TMOs) have been proven to play a critical role in promoting the formation and decomposition of Li2O2. Herein, a NiO/CNT catalyst was prepared by anchoring a NiO nanosheet on the surface of CNT. When using the NiO/CNT as a cathode catalyst, the Li-O2 battery had a lower overpotential of 1.2 V and could operate 81 cycles with a limited specific capacity of 1000 mA h g−1 at a current density of 100 mA g−1. In comparison, with CNT as a cathodic catalyst, the battery could achieve an overpotential of 1.64 V and a cycling stability of 66 cycles. The introduction of NiO effectively accelerated the generation and decomposition rate of Li2O2, further improving the battery performance. SEM and XRD characterizations confirmed that a Li2O2 film formed during the discharge process and could be fully electrochemical decomposed in the charge process. The internal network and nanoporous structure of the NiO/CNT catalyst could provide more oxygen diffusion channels and accelerate the decomposition rate of Li2O2. These merits led to the Li-O2 battery’s better performance.
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Mehrbod, Mohammad, Michela Martinelli, Caleb D. Watson, Donald C. Cronauer, A. Jeremy Kropf i Gary Jacobs. "Fischer-Tropsch Synthesis: The Characterization and Testing of Pt-Co/SiO2 Catalysts Prepared with Alternative Cobalt Precursors". Reactions 2, nr 2 (1.06.2021): 129–60. http://dx.doi.org/10.3390/reactions2020011.
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Different low-cost cobalt precursors (acetate, chloride) and thermal treatments (air calcination/H2 reduction versus direct H2-activation) were investigated to alter the interaction between cobalt and silica. H2-activated catalysts prepared from cobalt chloride had large Co0 particles (XRD, chemisorption) formed by weak interactions between cobalt chloride and silica (temperature programmed reduction (TPR), TPR with mass spectrometry (TPR-MS), TPR with extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectroscopy (XANES) techniques) and retained Cl-blocked active sites, resulting in poor activity. In contrast, unpromoted Co/SiO2 catalysts derived from cobalt acetate had strong interactions between Co species and silica (TPR/TPR-MS, TPR-EXAFS/XANES); adding Pt increased the extent of the Co reduction. For these Pt-promoted catalysts, the reduction of uncalcined catalysts was faster, resulting in larger Co0 clusters (19.5 nm) in comparison with the air-calcined/H2-activated catalyst (7.8 nm). Both catalysts had CO conversions 25% higher than that of the Pt-promoted catalyst prepared in the traditional manner (air calcination/H2 reduction using cobalt nitrate) and three times higher than that of the traditional unpromoted Co/silica catalyst. The retention of residual cobalt carbide (observed in XANES) from cobalt acetate decomposition impacted performance, resulting in a higher C1–C4 selectivity (32.2% for air-calcined and 38.7% for uncalcined) than that of traditional catalysts (17.5–18.6%). The residual carbide also lowered the α-value and olefin/paraffin ratio. Future work will focus on improving selectivity through oxidation–reduction cycles.
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Thompson, Simon T., i H. Henry Lamb. "Palladium-Rhenium Catalysts for Selective Hydrogenation of Furfural: Influence of Catalyst Preparation on Structure and Performance". Catalysts 13, nr 9 (25.08.2023): 1239. http://dx.doi.org/10.3390/catal13091239.
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PdRe/Al2O3 catalysts are highly selective for hydrogenation of furfural to furfuryl alcohol (FAL). Moreover, the synergy between the metals can result in greater specific activity (higher turnover frequency, TOF) than exhibited by either metal alone. Bimetallic catalyst structure depends strongly on the metal precursors employed and their addition sequence to the support. In this work, PdRe/Al2O3 catalysts were prepared by: (i) co-impregnation (CI) and sequential impregnation (SI) of γ-Al2O3 using HReO4 and Pd(NO3)2, (ii) SI using NH4ReO4 and [Pd(NH3)4(NO3)2], (iii) HReO4 addition to a reduced and passivated Pd/Al2O3 catalyst, and (iv) impregnation with the double complex salt (DCS), [Pd(NH3)4(ReO4)2]. Raman spectroscopy and temperature-programmed reduction (TPR) evidence larger supported PdO crystallites in catalysts prepared using Pd(NO3)2 than [Pd(NH3)4(NO3)2]. Surface [ReO4]− species detected by Raman exhibit TPR peak temperatures from ranging 85 to 260 °C (versus 375 °C for Re/Al2O3). After H2 reduction at 400 °C, the catalysts were characterized by chemisorption, temperature-programmed hydride decomposition (TPHD), CO diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and scanning transmission electron microscopy (STEM) with energy-dispersive x-ray (EDX) spectroscopy. The CI catalyst containing supported Pd–Re alloy crystallites had a TOF similar to Pd/Al2O3 but higher (61%) FAL selectivity. In contrast, catalysts prepared by methods (ii–iv) containing supported Pd-Re nanoparticles exhibit higher TOFs and up to 78% FAL selectivity.
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Wei, Zong Wu, Jian Hua Chen, Mei Qun Lin i Ye Chen. "Calcination Temperature Influence on the Microstructure and the Photocatalytic Properties of TiO2 Pillared Rectorite". Advanced Materials Research 197-198 (luty 2011): 790–95. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.790.
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TiO2 pillared rectorite (TPLR) had been synthesized by sol-gel method, and was characterized by XRD, TEM, BET, UV-vis DRS and FTIR. The effects of calcination temperature on the microstructure and the photocatalytic activity of the as prepared catalyst were investigated. The photocatalytic activity of the catalyst was evaluated by decomposition of Acid Red B (ARB) aqueous solution. XRD patterns revealed that TiO2 is incorporated into the interlayer of the rectorite. TEM demonstrated that TiO2 particles are present in the rectorite. The BET analysis indicated that the surface area of the sample calcined at 300°C (TPLR-300) was larger than those of other samples. The TPLR samples had high adsorption capacity and good photocatalytic efficiency in decomposition of ARB in water. FTIR spectra of the original and the recovered samples indicated that the catalyst had not chemically changed during the photocatalytic reaction.
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Courthéoux, Laurence, Dan Amariei, Sylvie Rossignol i Charles Kappenstein. "Thermal and catalytic decomposition of HNF and HAN liquid ionic as propellants". Applied Catalysis B: Environmental 62, nr 3-4 (luty 2006): 217–25. http://dx.doi.org/10.1016/j.apcatb.2005.07.016.
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Liu, Hua-Min, Xin-An Xie, Bing Feng i Run-Cang Sun. "Effect of catalysts on 5-lump distribution of constalk liquefaction in sub-critical ethanol". BioResources 6, nr 3 (17.05.2011): 2592–604. http://dx.doi.org/10.15376/biores.6.3.2592-2604.
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Liquefaction of cornstalk in sub-critical solution of ethanol without and with catalysts (K2CO3, Na2CO3 and ZnCl2) was performed in a stainless steel reactor (1 L) at temperatures of 200 to 300 oC. The cornstalk and the products of decomposition were divided into five lumps (gas, organic dissolved, heavy oil, volatile organic compounds, and residue). The effects of reaction temperature and the catalyst amount on the five lump yields were studied. The bio-oils produced with and without catalysts were characterized by GC/MS. Results showed that an increment in the temperature and the addition of catalysts had a synergetic effect on the lumps yield as compared to the non-catalytic experiments, and different catalytic procedures had an important effect on the lump yields and compounds of the bio-oils. The addition of the catalyst enhanced the gas yield and the total conversion rate. A high temperature, lower amount of Na2CO3, moderate amount of K2CO3, and a high amount of ZnCl2 were propitious to enhance the heavy oil. The formation of volatile organic compounds with the presence of ZnCl2 and K2CO3 was less than that in non-catalytic experiments at the higher temperatures. However, a higher conversion temperature had a negative impact on the bio-oils yield from liquefaction of cornstalk with and without catalysts.
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Gong, Xingfan, Jiacheng Xu, Tiantian Zhang, Yan Sun, Shiyu Fang, Ning Li, Jiali Zhu i in. "DRIFTS-MS Investigation of Low-Temperature CO Oxidation on Cu-Doped Manganese Oxide Prepared Using Nitrate Aerosol Decomposition". Molecules 28, nr 8 (16.04.2023): 3511. http://dx.doi.org/10.3390/molecules28083511.
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Cu-doped manganese oxide (Cu–Mn2O4) prepared using aerosol decomposition was used as a CO oxidation catalyst. Cu was successfully doped into Mn2O4 due to their nitrate precursors having closed thermal decomposition properties, which ensured the atomic ratio of Cu/(Cu + Mn) in Cu–Mn2O4 close to that in their nitrate precursors. The 0.5Cu–Mn2O4 catalyst of 0.48 Cu/(Cu + Mn) atomic ratio had the best CO oxidation performance, with T50 and T90 as low as 48 and 69 °C, respectively. The 0.5Cu–Mn2O4 catalyst also had (1) a hollow sphere morphology, where the sphere wall was composed of a large number of nanospheres (about 10 nm), (2) the largest specific surface area and defects on the interfacing of the nanospheres, and (3) the highest Mn3+, Cu+, and Oads ratios, which facilitated oxygen vacancy formation, CO adsorption, and CO oxidation, respectively, yielding a synergetic effect on CO oxidation. DRIFTS-MS analysis results showed that terminal-type oxygen (M=O) and bridge-type oxygen (M-O-M) on 0.5Cu–Mn2O4 were reactive at a low temperature, resulting in-good low-temperature CO oxidation performance. Water could adsorb on 0.5Cu–Mn2O4 and inhibited M=O and M-O-M reaction with CO. Water could not inhibit O2 decomposition to M=O and M-O-M. The 0.5Cu–Mn2O4 catalyst had excellent water resistance at 150 °C, at which the influence of water (up to 5%) on CO oxidation could be completely eliminated.
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Yamanaka, Ichiro, Yuta Nabae i Takeo Ito. "Effect of an Oxides Composite Support of Ce(Sm)O3-La(Sr)CrO3 on Pd-Ni Alloy for Decomposition Activity of CH4". Advances in Science and Technology 65 (październik 2010): 215–24. http://dx.doi.org/10.4028/www.scientific.net/ast.65.215.
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A Pd-Ni/La(Sr)CrO3-Ce(Sm)O2 composite anode showed good performance for solid oxide fuel cell reactions with dry CH4. Compositions of Pd and Ni in the Pd-Ni/La(Sr)CrO3-Ce(Sm)O2 composite anode affected the electrochemical oxidation catalysis of dry CH4. The Pd and Ni ratios from 50:50 to 75:25 were suitable for the oxidation. The Pd-Ni/La(Sr)CrO3-Ce(Sm)O2 composite anode showed the high tolerance to the carbon deposition under closed and open circuit conditions. A Pd-Ni/Ce(Sm)O2 catalyst showed very low catalytic activity for decomposition of dry CH4. A Pd-Ni/SiO2 catalyst showed very high catalytic activity for the decomposition of dry CH4 and a large amount of deposited carbon formed. The Pd-Ni particles on SiO2 were quite multifaceted from TEM-EDS observation. On the other hand, the Pd-Ni particles on Ce(Sm)O2 support had a spherical shape and doping of Ce and Sm was confirmed. This nature should inhibit the formation of particular plane that is essential for the carbon fiber formation. The detail function of Ce(Sm)O2 and La(Sr)CrO3 supports was discussed.
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Shen, Hong, Zijun Tang, Xiang Xiao, Haiwen Wu, Hang Zhou, Ping Fang, Dingfang Zhu i Jianhua Ge. "Catalytic Oxidation of NO by Ozone over Mn-Ce/Al2O3/TiO2 Catalyst". Processes 10, nr 10 (27.09.2022): 1946. http://dx.doi.org/10.3390/pr10101946.
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In this study, Mn-Ce/Al2O3/TiO2 catalyst prepared by impregnation method was used for synergistic O3 oxidation NO. The catalyst prepared by impregnating Al2O3/TiO2 at a Mn:Ce molar ratio of 4:1 showed the best catalytic activity. The catalyst performance showed that when the molar ratio of Mn:Ce was 4:1 and the volume ratio of O3:NO was 1:4, the removal rate of NO could reach 63%, which could increase the removal rate by 40% compared with that of NO oxidized by O3 alone. BET, XRD, and TEM characterization results showed that when the molar ratio of Mn:Ce was 4:1, the catalyst specific surface area, and pore capacity were the largest. A large amount of MnOx and CeOx were distributed on the catalyst surface. The XPS analysis showed that the oxidation-reduction and oxygen vacancy of Mn (IV)/Mn (III)/Mn (II) and Ce (IV)/Ce (III), had a synergistic effect on the decomposition of O3 into reactive oxygen species(O*), thus improving the catalytic capacity of Mn-Ce/Al2O3/TiO2 catalyst for O3. The O2-TPD analysis showed that the oxygen vacancies and oxygen species in the catalyst could be used as the active point of decomposition of O3 into O*. The experimental results show that the prepared catalyst can significantly improve the efficiency of ozone oxidation of NO and reduce the amount of ozone. The catalyst can be applied to ozone oxidation denitrification technology.
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Liu, Hongfeng, Xingrui Fu, Xiaole Weng, Yue Liu, Haiqiang Wang i Zhongbiao Wu. "Catalytic Combustion of Low Concentration Methane over Catalysts Prepared from Co/Mg-Mn Layered Double Hydroxides". Journal of Chemistry 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/751756.
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A series of Co/Mg-Mn mixed oxides were synthesized through thermal decomposition of layered double hydroxides (LDHs) precursors. The resulted catalysts were then subjected for catalytic combustion of methane. Experimental results revealed that the Co4.5Mg1.5Mn2LDO catalyst possessed the best performance with theT90=485°C. After being analyzed via XRD, BET-BJH, SEM, H2-TPR, and XPS techniques, it was observed that the addition of cobalt had significantly improved the redox ability of the catalysts whilst certain amount of magnesium was essential to guarantee the catalytic activity. The presence of Mg was helpful to enhance the oxygen mobility and, meanwhile, improved the dispersion of Co and Mn oxides, preventing the surface area loss after calcination.
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Yu, Li Yan, Li Na Sui i Zuo Lin Cui. "Synthesis of Carbon Nanofibers: A Catalyst Derived from Cupric Carbonate Basic during Acetylene Decomposition". Materials Science Forum 610-613 (styczeń 2009): 579–84. http://dx.doi.org/10.4028/www.scientific.net/msf.610-613.579.
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Two types of helical and straight carbon nanofibers, have been synthesized by the decomposition of acetylene using cupric carbonate basic as catalyst precursor at low temperature. The obtained carbon nanomaterials were characterized by transmission electron microscope, scanning electron microscope, and X-ray power diffraction. The size of the catalyst nanoparticles remaining inside the resultant nanofibers was determined. The carbon nanofiber diameters, ranging from 30 to 400 nm, closely correlated with the size of the catalytic nanoparticle. The growth mechanism of carbon nanomaterials was also studied. The nanocopper particle size had a considerable effect on the morphology of carbon nanofibers. The helical carbon nanofibers with a symmetric growth mode were synthesized with the nanocopper catalyst particles having a grain size less than 50 nm. When the average catalyst particle size determined was around 50–300 nm, the straight carbon nanofibers were obtained dominantly.
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Du, Qiang, Tian Tian Xu, Xue Mei Song, Ying Zhang, Yang Liao i Shi Lin Zhao. "Preparation of Fibrous SO42-/ZrO2-Nio Solid Acid Catalyst, Characterization and its Catalytic Properties". Advanced Materials Research 518-523 (maj 2012): 873–77. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.873.
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A novel SO42-/ZrO2-NiO solid acid catalyst was prepared by using collagen fiber as the template. It was found that the SO42-//sup>ZrO2-NiO catalyst remained good fibrous morphology by scanning electron microscopy (SEM). The IR analysis suggested that the metal oxide surface and SO42-were combined to form dual-coordinate state. The catalyst had both medium strong acidic sites and strong acidic sites through temperature-programmed decomposition (TPD) of ammonia. The calcination temperature is inversely proportional to the surface area of fibrous ZrO2-NiO. The catalyst was applied to the esterification of acetic acid with n-butanol to estimate the catalytic activity and the best preparation conditions of SO42-/ZrO2-NiO solid acid catalyst was found out. The results showed the SO42-/ZrO2-NiO catalyst had high catalytic activity.
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Hong, Sunghoon, Sujeong Heo, Wooram Kim, Young Jo, Young-Kwon Park i Jong-Ki Jeon. "Catalytic Decomposition of an Energetic Ionic Liquid Solution over Hexaaluminate Catalysts". Catalysts 9, nr 1 (14.01.2019): 80. http://dx.doi.org/10.3390/catal9010080.
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The objective of this study was to determine the effect of a synthesis procedure of Sr hexaaluminate on catalytic performance during the decomposition of ionic liquid monopropellants based on ammonium dinitramide (ADN) and hydroxyl ammonium nitrate (HAN). Sr hexaaluminates were prepared via both coprecipitation and a sol–gel process. The surface area of hexaaluminate synthesized via the coprecipitation method was higher than that of hexaaluminate synthesized by the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is because of the sintering of α-Al2O3 on the hexaaluminate synthesized via the sol–gel process, which could not be observed on the catalysts synthesized via the coprecipitation method. The hexaaluminate synthesized via coprecipitation showed a lower decomposition onset temperature during the decomposition of ADN- and HAN-based liquid monopropellants in comparison with the catalysts synthesized via the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is attributed to the differences in the Mn3+ concentration and the surface area between the two hexaaluminates. Consequently, the hexaaluminate synthesized via coprecipitation which calcined above 1200 °C showed high activity during the decomposition of energetic ionic liquid monopropellants compared with the hexaaluminate synthesized via the sol–gel process.
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Lin, Jih-Gaw, Cheng-Nan Chang, Jer-Ren Wu i Ying-Shih Ma. "Enhancement of decomposition of 2-chlorophenol with ultrasound/H2O2 process". Water Science and Technology 34, nr 9 (1.11.1996): 41–48. http://dx.doi.org/10.2166/wst.1996.0173.
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We investigated the effects of pH, ionic strength, catalyst, and initial concentration on both decomposition of 2-chlorophenol (2-cp) and removal of total organic carbon (TOC) in aqueous solution with ultrasonic amplitude 120 μm and H2O2 (200 mg/l). When the initial concentrations of 2-cp was 100 mg/l and the pH was controlled at 3, the rate of 2-cp decomposition was enhanced up to 6.6-fold and TOC removal up to 9.8-fold over pH controlled at 11. At pH 3, the efficiency of decomposition of 2-cp was 99% but the removal of TOC was only 63%; a similar situation applied at pH 7 and 11. Hence intermediate compounds were produced and 2-cp was not completely mineralized. When the concentration of ionic strength was increased from 0.001 to 0.1 M, the rate of 2-cp decomposition was enhanced only 0.3-fold, whereas the TOC removal was not enhanced. In comparison of the effects of pH and ionic strength, pH had greater influence on both 2-cp decomposition and TOC removal than ionic strength. The effect of a catalyst (FeSO4) on decomposition of 2-cp was insignificant comparing with direct addition of H2O2. The reaction rate at a smaller initial concentration of 2-cp (10 mg/l) was more rapid than at a greater one (100 mg/l). The rate of 2-cp decomposition and TOC removal appeared to follow pseudo-first-order reaction kinetics.
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Chesnokov, Vladimir V., Vladimir V. Kriventsov, Igor P. Prosvirin i Evgeny Yu Gerasimov. "Effect of Platinum Precursor on the Properties of Pt/N-Graphene Catalysts in Formic Acid Decomposition". Catalysts 12, nr 9 (8.09.2022): 1022. http://dx.doi.org/10.3390/catal12091022.
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Properties of a novel catalytic material, Pt/N-graphene, in gas-phase decomposition of formic acid to obtain pure hydrogen were studied. The graphene powder doped with nitrogen atoms was used as the carbon support. The following methods were used to characterize the synthesized catalysts: X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), EXAFS and CO chemisorption. It was determined that the platinum precursor substantially affects the state of the metal in the Pt/N-graphene catalysts. When Pt(NO3)4 was used as the precursor, platinum on the catalyst surface was in the form of nanocrystals. Meanwhile, the use of H2PtCl6 led to the formation of atomically dispersed platinum stabilized on the surface of N-graphene. Carbon structures containing defects in the graphene layer surrounded by four nitrogen atoms had strong interactions with platinum atoms and acted as the sites where atomic platinum was stabilized.
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Wang, Jun Hu, i Toru Nonami. "Comparison of Adsorption Capability and Photocatalytic Activity for Methylene Blue Decomposition of LiInO2 with NaInO2". Key Engineering Materials 317-318 (sierpień 2006): 819–22. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.819.
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In the present study, Pt, NiO, and RuO2 fine particles as co-catalyst were loaded on the LiInO2 surface by different methods for enhancing its adsorption capability and photocatalytic activity for methylene blue dye (MB) decomposition. Clear adsorption capability and marked photocatalytic activity for MB decomposition were confirmed on the co-catalyst loaded LiInO2 composite particles. Comparing with that of LiINO2, the previously reported NaInO2 photocatalyst had stronger adsorption capability and higher photocatalytic activity. However, the adsorption capabilities and the photocatalytic activities were separately in the same order of RuO2/AInO2 > Pt/AInO2 > AInO2 > NiO/AInO2 and Pt/LiInO2 > RuO2/LiInO2 > NiO/LiInO2 > LiInO2 for the two promising AInO2 (A = Li+ or Na+) photocatalyst.
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Wu, Deli, Yanxia Liu, Dong Duan i Luming Ma. "Pyrite cinder as a cost-effective heterogeneous catalyst in heterogeneous Fenton reaction: decomposition of H2O2 and degradation of Acid Red B". Water Science and Technology 70, nr 9 (29.09.2014): 1548–54. http://dx.doi.org/10.2166/wst.2014.389.
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Pyrite cinder (PyC) was employed as a heterogeneous Fenton-like catalyst, and its catalytic activity was evaluated in view of the effects of catalyst dosage, pH and leaching metal ions. PyC showed significant reactivity, and the pseudo-first-order kinetic rate constant for decomposition of H2O2 and degradation of Acid Red B (ARB) were 3.4 and 14.89 (10−3 min−1) respectively when pH = 5. When 20 g/L PyC was added into 10 mM H2O2 solution in neutral pH, H2O2 could be completely degraded within 4 h, and more than 90% ARB was removed. Leaching metal ions from PyC were found to have little effect on decomposition of H2O2 or on degradation of ARB. PyC still had high catalytic activity after five successive runs. The decomposition mechanism of H2O2 was analyzed and the Haber–Weiss mechanism was employed in this paper. The electron spin resonance image showed •OH was produced and increased between 3 and 5 min in the PyC catalyzing H2O2 reaction, which demonstrated that PyC had a durable ability to produce •OH.
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Queiroz, Maria Aparecida Ribeiro, i Josimar Ribeiro. "Catalysts of PtSn/C Modified with Ru and Ta for Electrooxidation of Ethanol". Catalysts 9, nr 3 (18.03.2019): 277. http://dx.doi.org/10.3390/catal9030277.
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PtSn/C-type catalysts modified with Ta and Ru were prepared by the thermal decomposition of polymeric precursors with the following nominal compositions: Pt70Sn10Ta20/C, Pt70Sn10Ta15Ru5/C, Pt70Sn10Ta10Ru10/C and Pt70Sn10Ta5Ru15/C. The physicochemical characterization was performed by X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical characterization was performed using cyclic voltammetry, chronoamperometry and fuel cell testing. PtSnTaRu/C catalysts were characterized in the absence and presence of ethanol in an acidic medium (H2SO4 0.5 mol L−1). All the catalysts showed activity for the oxidation of ethanol. The results indicated that the addition of Ta increased the stability and performance of the catalysts, as the Pt70Sn10Ta20/C catalyst had the maximum power density of 27.3 mW cm−2 in an acidic medium. The results showed that the PtSn/C-type catalysts modified with Ta and Ru showed good performance against alcohol oxidation, representingan alternative to the use of direct ethanol fuel cells.
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Pang, Xinzhu, Nathan Skillen, Detlef W. Bahnemann, David W. Rooney i Peter K. J. Robertson. "Photocatalytic H2O2 Generation Using Au-Ag Bimetallic Alloy Nanoparticles loaded on ZnO". Catalysts 12, nr 9 (24.08.2022): 939. http://dx.doi.org/10.3390/catal12090939.
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Hydrogen peroxide (H2O2) is an important chemical as it is an environmentally friendly oxidant for organic synthesis and environmental remediation as well as a promising candidate for the liquid fuel. Photocatalytic generation of H2O2 is sustainable, and many efforts have been put into the development of new catalysts to gain high H2O2 yields. In this investigation, Au/ZnO, Ag/ZnO and Au-Ag/ZnO catalysts were prepared by the simultaneous impregnation of HAuCl4 and AgNO3 and they were used to generate H2O2 from a methanol/O2 system. It was demonstrated that Au/ZnO had the best performance at generating H2O2. The presence of Au on ZnO accelerated the generation of H2O2 on ZnO and facilitated H2O2 adsorption onto the catalyst surface, which resulted in the reaction kinetics changing from zero-order to first-order. Ag atoms on Ag/ZnO were unstable and would strip from the surface of ZnO during irradiation, decreasing the yield of H2O2. The stabilization of Ag on Au-Ag/ZnO depended on the ratio of Au and Ag. Au0.1Ag0.2/ZnO was a stable catalyst and it showed that the presence of Ag promoted the formation and decomposition of peroxide, simultaneously.
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Park, Ji Hwan, Sung Gab Kim, Seong Soo Park, Seong Soo Hong i Gun Dae Lee. "Photocatalytic Oxidation and Decomposition of Acetic Acid over TiO2, TS-1 and Ti-MCM-41 Catalysts". Materials Science Forum 510-511 (marzec 2006): 34–37. http://dx.doi.org/10.4028/www.scientific.net/msf.510-511.34.
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Transient reaction of adsorbed monolayer of acetic acid was used to compare the photocatalytic properties of TiO2 (Degussa P-25), titanium silicalite (TS-1) and Ti-MCM-41. TS-1 and Ti-MCM-41 catalysts with Si/Ti ratio of 50 were prepared by in-situ crystallization. The catalysts were characterized using XRD and UV-DRS. During photocatalytic oxidation (PCO), CO2 and HCHO were formed on P-25 TiO2, whereas CO2 and CH4 formed on TS-1 and Ti-MCM-41. Acetic acid decomposed photocatalytically on P-25 TiO2 to form CO2, CH4 and C2H6. On the contrary, CO2 and CH4 were formed on TS-1 and Ti-MCM-41 during photocatalytic decomposition (PCD). The rates of product formation during PCD were lower than PCO. The TS-1 and Ti- MCM-41 catalysts were less active per gram of catalyst. However, the TS-1 and Ti-MCM-41 catalysts had much higher adsorption capacities for organics. Therefore, it seems that the TS-1 and Ti-MCM-41 catalysts have some advantages in applications to PCO of organic comtaminants under conditions where the organic concentrations vary widely.
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Irada Ahmadova, Irada Ahmadova. "WHEN CHOOSING CATALYSTS FOR THE CONVERSION OF ISOBUTYLENE PRINCIPLES OF QUALITY AND QUANTITY". PAHTEI-Procedings of Azerbaijan High Technical Educational Institutions 11, nr 07 (5.11.2021): 29–34. http://dx.doi.org/10.36962/pahtei1107202129.
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Catalysts play an extremely important role in wildlife and industry. Today it is difficult to describe chemistry and petrochemistry without catalytic processes. Catalytic processes account for 80-85% of oil refining. Therefore, the problem of choosing a catalyst is of interest both from the point of view of quality and quantity. In this paper, the activity of a high silicon zeolite catalyst used in the conversion of isobutene was studied at various temperatures, and it was determined that a sample of the zeolite catalyst during the process initially had no catalytic activity during the conversion of isobutene. The release of liquid products is observed only after the formation of 5-8% of compaction products (PM) on the surface within 25-30 minutes from the beginning. Consequently, modifiers have a positive effect on catalytic activity. In this case, the number and strength of the acid sites of the catalyst changes. The study of isobutene conversion process showed that the formation of liquid products is observed at 150°C. It was shown that in this case in the temperature range 150°C-300°C liquid products of isobutene reaction consist of primarily from aliphatic and at 350°C- 450°C from aromatic hydrocarbons. The process of conversion of hexane-1 on the high-silica zeolite catalyst is studied and it was shown that the decomposition of hexene-1 into ethene and propene is occure at the beginning, at 250°C and then the process takes place in a mixture of the two olefins. It was shown by the using of XRD, TG/DTA methods, that the formed products of seals in the conversion of isobutene and 1-hexene over the high silica zeolite catalyst,is composed of two phases that differ from each other in thermal stability. The obtained liquid products during the conversion of isobutene at 150°C-300°C can be used as high-octane gasoline fractions as motor fuel component. The adsorbed NH3 probe molecules method showed that during the conversion of propene, isobutene and hexene-1, the amount of acid sites of spent catalysts is reduced by 43-50%. In this state, the catalyst exhibits high catalytic activity. Keywords: catalyst, activity, isobutene, zeolite.
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Hall, J. B., i E. H. Hirschherg. "MgO Passivation of Vanadium on Cracking Catalyst". Proceedings, annual meeting, Electron Microscopy Society of America 45 (sierpień 1987): 200–201. http://dx.doi.org/10.1017/s0424820100125907.
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Vanadium, which is present in crude oil as metal porphyrins, builds up on cracking catalyst during use and is believed to cause decomposition of the faujasite component. The addition of magnesia (MgO) to cracking catalyst is thought to passivate the vanadium thereby prolonging catalyst life. An analytical electron microscope (AEM) investigation was undertaken to gain an understanding of the passivation mechanism.The base catalyst used in this study was composed of faujasite and an amorphous silica-alumina. Test samples were prepared by mixing steamed cracking catalyst with MgO, impregnating the mixture with vanadium and nickel naphthenates, drying at 250°F, calcining at 1000°F, and steaming at 1400°F. The two samples used for the AEM study each had final compositions of 1000 ppm Ni and 3000 ppm V, but contained levels of 30 and 3% MgO.
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Castro-León, Gabriela, Erik Baquero-Quinteros, Bryan G. Loor, Jhoselin Alvear, Diego E. Montesdeoca Espín, Andrés De La Rosa i Carolina Montero-Calderón. "Waste to Catalyst: Synthesis of Catalysts from Sewage Sludge of the Mining, Steel, and Petroleum Industries". Sustainability 12, nr 23 (25.11.2020): 9849. http://dx.doi.org/10.3390/su12239849.
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The generation of sewage sludge presents a problem for several manufacturing companies as it results from industrial processes or effluent treatment systems. The treatment of this type of waste requires high economic investment, for this reason, it is necessary to find alternatives to recover the valuable materials of the sludges. In this study, metal catalysts were synthesized using waste sludge from the steel, mining, and hydrocarbon industries. The waste sludge was subjected to thermal treatments for the removal of organic content and the reduction of metals with hydrogen current to activate their catalytic properties. The sludge and synthesized catalysts were analyzed to determine their physical, chemical, thermoenergetic, and catalytic properties. Catalytic activity was evaluated using CO chemisorption and by thermal–catalytic decomposition of crude oil. The best conditions for synthesizing the catalysts were a calcination temperature between 300 and 500 °C and a reduction temperature between 300 and 900 °C. The catalysts presented a specific surface between 2.33 and 16.78 m2/g. The catalytic material had a heat capacity between 0.7 and 1.2 kJ/kg∙K. The synthesized materials presented catalytic activity comparable to that of commercial catalysts. With this recovery technique, the industrial waste can be valorized, obtaining catalyst derived from the sludges and promoting the circular economy of manufacturing companies.
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Song, Jun, Wen Long Jian i Li Wang. "Study on Thermal Analysis Kinetics of Carbon Support". Advanced Materials Research 750-752 (sierpień 2013): 1322–25. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.1322.
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Actived carbon can be widely used as adsorbent, catalyst and catalyst support for many chemical reactions. At present, the research on thermal analysis Kinetics of actived carbon is quite few.Studing on it,is helpful for disclosing the decomposition reaction process and thermodynamic law of actived carbon. By thermal analysis, thermal decomposition Characteristics of actived carbon is studied. The TG and DTG eurves of actived carbon were obtain ed using multiple heating rate method.The test data were processed by iso-conversional method to obtain the kinetic parameters.The results showed that, with the improving of heating rate , the startimg reaction temperature of TG and the peak temperature of DTG shifted to the high temperature zone, postponement phenomena occurred.Based on the collected experimental data, it proved that had better linear relations with . The activation energy E of decomposition reaction of actived carbon, which was determined by measurements of slope, was 96.59kJ/mol. The plot of vs was drew and a straight line was obtained. .The mechanism function was defined as ,so according to the slope and intercept of the line,it can be obtained that n=3.585,A=40189.85984.
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Lei, Bowen, Jie Wen, Shan Ren, Lianhong Zhang i Hui Zhang. "Highly efficient COx-free hydrogen evolution activity on rod Fe2N catalysts for ammonia decomposition". New Journal of Chemistry 43, nr 46 (2019): 18277–84. http://dx.doi.org/10.1039/c9nj04273c.
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Albayati, Talib M., i Aidan M. Doyle. "SBA-15 Supported Bimetallic Catalysts for Enhancement Isomers Production During n-Heptane Decomposition". International Journal of Chemical Reactor Engineering 12, nr 1 (1.01.2014): 345–54. http://dx.doi.org/10.1515/ijcre-2013-0120.
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Abstract Santa Barbara Amorphous (SBA)-15 supported 1% (Pt–Ni), 1% (Pt–Co) and 1% (Ni–Co) bimetallic catalysts in a heterogeneous reaction for enhancement hydroisomerization and hydrocracking production during reforming or decomposition of n-heptane. The structural and textural features of the nanoporous silicas, both with and without encapsulated nanoparticles, were characterized using small-angle X-ray diffraction, scanning electron microscopy, EDAX, nitrogen adsorption–desorption porosimetry (Brunauer–Emmett–Teller) surface area analysis, Fourier-transform infrared spectroscopy and transmission electron microscopy. The catalytic performance was evaluated at 250–400°C under atmospheric pressure in a plug-flow reactor in a catalyst testing rig under tightly controlled conditions of temperature, reactant flow rate and pressure. The species leaving the reactor were analysed by Gas Chromatography. The results show that 1% (Pt–Ni)/SBA-15, 1% (Pt–Co)/SBA-15 and 1% (Ni–Co)/SBA-15 had a high activity for conversion of n-heptane (around 85%). The selectivity of isomerization is not high, so further studies have to be carried out in the future.
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Singh, Harsimranjit, Shiqiang Zhuang, Bharath Nunna i Eon Lee. "Thermal Stability and Potential Cycling Durability of Nitrogen-Doped Graphene Modified by Metal-Organic Framework for Oxygen Reduction Reactions". Catalysts 8, nr 12 (3.12.2018): 607. http://dx.doi.org/10.3390/catal8120607.
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Here we report a nitrogen-doped graphene modified metal-organic framework (N-G/MOF) catalyst, a promising metal-free electrocatalyst exhibiting the potential to replace the noble metal catalyst from the electrochemical systems; such as fuel cells and metal-air batteries. The catalyst was synthesized with a planetary ball milling method, in which the precursors nitrogen-functionalized graphene (N-G) and ZIF-8 are ground at an optimized grinding speed and time. The N-G/MOF catalyst not only inherited large surface area from the ZIF-8 structure, but also had chemical interactions, resulting in an improved Oxygen Reduction Reaction (ORR) electrocatalyst. Thermogravimetric Analysis (TGA) curves revealed that the N-G/MOF catalyst still had some unreacted ZIF-8 particles, and the high catalytic activity of N-G particles decreased the decomposition temperature of ZIF-8 in the N-G/MOF catalyst. Also, we present the durability study of the N-G/MOF catalyst under a saturated nitrogen and oxygen environment in alkaline medium. Remarkably, the catalyst showed no change in the performance after 2000 cycles in the N2 environment, exhibiting strong resistance to the corrosion. In the O2 saturated electrolyte, the performance loss at lower overpotentials was as low compared to higher overpotentials. It is expected that the catalyst degradation mechanism during the potential cycling is due to the oxidative attack of the ORR intermediates.
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Ngo, Ha-Son, Thi-Linh Nguyen, Ngoc-Tuan Tran i Hanh-Chi Le. "Photocatalytic Removal of Ciprofloxacin in Water by Novel Sandwich-like CuFe2O4 on rGO/Halloysite Material: Insights into Kinetics and Intermediate Reactive Radicals". Water 15, nr 8 (17.04.2023): 1569. http://dx.doi.org/10.3390/w15081569.
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In this study, the CuFe2O4 on rGO/halloysite material was made in an uncomplicated manner. The catalyst has a sandwich-like shape with a uniform coating of the active phase on the rGO sheets and halloysite tubes. The catalyst’s large specific surface area (130 m2/g) and small band gap energy (1.9 eV) allow it to adsorb photons and photocatalyze organic contaminants effectively. In approximately 1 h of light, the catalyst showed high performance in achieving almost complete conversion in photodegrading CIP for an initial CIP concentration of 20 ppm. A pseudo-first-order rate law was followed by the process, as revealed by the experimental results. In addition, the pH effect and the contribution of intermediate reactive radicals that emerged during the photochemical process were explored. The results indicated that hydroxyl radicals and holes had a major impact on CIP decomposition, suggesting that the addition of these radicals could enhance CIP degradation efficiency at a larger scale. This study also confirmed the superiority of catalysis and photochemical processes in environmental treatments by the neutral pH values.
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Korobova, Arina, Nikolay Gromov, Tatiana Medvedeva, Alexander Lisitsyn, Lidiya Kibis, Olga Stonkus, Vladimir Sobolev i Olga Podyacheva. "Ru Catalysts Supported on Bamboo-like N-Doped Carbon Nanotubes: Activity and Stability in Oxidizing and Reducing Environment". Materials 16, nr 4 (9.02.2023): 1465. http://dx.doi.org/10.3390/ma16041465.
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The catalysts with platinum-group metals on nanostructured carbons have been a very active field of research, but the studies were mainly limited to Pt and Pd. Here, Ru catalysts based on nitrogen-doped carbon nanotubes (N-CNTs) have been prepared and thoroughly characterized; Ru loading was kept constant (3 wt.%), while the degree of N-doping was varied (from 0 to 4.8 at.%) to evaluate its influence on the state of supported metal. Using the N-CNTs afforded ultrafine Ru particles (<2 nm) and allowed a portion of Ru to be stabilized in an atomic state. The presence of Ru single atoms in Ru/N-CNTs expectedly increased catalytic activity and selectivity in the formic acid decomposition (FAD) but had no effect in catalytic wet air oxidation (CWAO) of phenol, thus arguing against a key role of single-atom catalysis in the latter case. A remarkable difference between these two reactions was also found in regard to catalyst stability. In the course of FAD, no changes in the support or supported species or reaction rate were observed even at a high temperature (150 °C). In CWAO, although 100% conversions were still achievable in repeated runs, the oxidizing environment caused partial destruction of N-CNTs and progressive deactivation of the Ru surface by carbonaceous deposits. These findings add important new knowledge about the properties and applicability of Ru@C nanosystems.